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 # Database
 
-A MySQL database is required for dn42peering central to work. Before installing the central program, make sure you have a proper database with tables setup.
+A MySQL database is required for dn42peering central to work. Before installing the central program, make sure you have a proper database with necessary privileges setup.
 
-Here is the SQL used to setup a production database:
+Create a database and user, then grant it with all data and structure privileges. The server will automatically create tables and upgrade schema in the future.
 
-See [0-init.sql](sql/0-init.sql) for creating initial schema.
+## Auto Migration
 
-Note that the SQL script will update with schema updates. Please follow the docs/sql/ with the latest version.
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+The server will migrate database schema before starts. All migration SQL files can be found in the resources.
+
+In case migration fails, the server will return an exception with instructions and exit.
+
+Follow the instructions and combine it with the SQL files to solve the problem yourself.
+
+For example, a duplicated column name may be caused by duplicated SQL statements. In this case, delete the column may fix the problem.
+
+After manually inspection, change the migration action to `repair`. In this mode, the server automatically rolls back the history and becomes ready to retry.
+
+The server will never fix database errors itself. Repair mode only rolls back history and version state.
+
+### Migrate modes
+
+```json
+{
+  "database": {
+    "migrate": "auto"
+  }
+}
+```
+
+Case-insensitive.
+
+* **auto**: Default mode. The server will automatically upgrades the schema.
+* **auto_no_baseline**: Similar to `auto`, but will not set the version to 3 (which is the last schema version before implementing migration) if the database is not empty but does not have a history record. In this case, it will fail.
+* **disabled**: Not recommended. Disable all migration and start silently. This may led to schema errors.
+* **repair**: Repair the history record after incomplete migrations. The server will only roll back history state and exit. Use this as an oneshot action after manually fixing database structure. Good luck!
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